A variety of nuts, including shelled fruits and seeds, have been widely used as edible ingredients of sweets and foods. After extracting the edible portions from the harvested nuts (portions after being removed from the shells), raw material nuts or processed nuts after being roasted are used for a variety of purposes. The nuts available include those which maintain their shape after they are taken out of the shells (whole nuts), those in a paste form, or those in a powder form. In other cases, they are often processed in a variety of sizes such as grains or small fragments which are suitable for their respective purposes. When nuts are used as secondary ingredients in food manufacturing as in the manufacturing of sweets or breads, they are generally provided in very small fragments (grains). To prepare small nut fragments, mechanical force is typically applied using a variety of types of grinders or cutters. If the raw materials contain large amounts of oily components, such as in pecans, macadamia nuts, peanuts, hazelnuts, etc., the conventional method of producing ground products in desirable sizes is by selecting either a forced grinding method using metallic rollers, or a chopping method using an appliance having a sharp cutter. The grinding can be performed by passing the nuts between two toothed rollers or between a roller and a toothed plate, and the cutting can be performed by using a sharp, thick blade to cut off pieces of hard textured nuts.
In the conventional mechanical separation using a grinder or a cutter, the production of undesirable powder or small particles generally cannot be avoided during the grinding process. In addition, it has been difficult to efficiently process the nut fragments into desired sizes. In addition, when the nuts have a high oil content, the ratio of powder or unusable scrap particles to the desired nut fragments produced during grinding increases. As the cost of the raw materials (nuts) increases, the value lost through the production of unusable scraps increases. Therefore, a major subject of concern is that the prices of the chopped nut fragments greatly depend upon whether these byproducts, for example, the secondary products prepared by crushing into a paste form, can be expected to have high demand.
Another result of conventional mechanical grinding techniques is that the compression of the raw material nuts when grinding the nuts causes the oil contents in the raw material nuts to leach out. As a result, the small nut fragments present an oily finish. This can cause premature deterioration in the quality of the nut fragments.